The present invention relates to a system for local transmission of signals, such as television signals, audio signals, and the like, and more particularly to a wireless local signal transmission system for transmitting signals at frequencies above 900 Mhz.
Audio and television equipment for home use is becoming increasingly complex, involving multiple programming sources. Many homes typically have more than one television and more than one stereophonic audio system in order to provide viewing and listening capability in more than one room in the home. If it is desired to provide viewing and listening capability in more than one room in the home from an exterior antenna or a CATV service it has been necessary heretofore to hardwire television antenna leads, either 300 ohm twin lead or 75 ohm coaxial cable between the source of the signal as it enters the home and each of the receivers at which reception is desired. It has also been necessary to have separate VCRs and video disk players at each location where such programming was desired.
It has recently been proposed to employ local signal transmission systems operating within a frequency band of 902 MHz to 928 MHz for transmitting television signals locally from a programming source to a remote television receiver. See U.S. Pat. No. 4,916,532 issued Apr. 10, 1990.
However, the practical implementation of wireless local signal transmission system operating in the 902 MHz to 928 MHz frequency band is problematical in a number of respects. Transmitter power is limited to 500 microwatts and the transmitter must employ a quarter wave transmitting antenna, so that the signal is transmitted at a very low level, thus severely limiting the local transmission range.
Local transmission receivers heretofore provided for use in the 902 MHz to 928 MHz frequency band exhibit limited selectivity so that it has not been possible to practically transmit and receive a plurality of signals transmitted at different frequencies within the local transmission band. This presents a serious limitation on the usefulness of such local signal transmission systems, as it is not possible to transmit signals from a plurality of sources simultaneously.